Using methodology we developed we found increased plasma DOPA in all patients studied with neuroblastoma and in most patients with malignant pheochromocytoma. DOPA, norepinephrine (NE), and dopamine (DA) are detectable in vivo in human cerebral cortex, and levels of these substances are increased in epileptogenic foci. Neuroendocrine responses to a real-life stress (removal of third molars) in humans include increases in plasma beta-endorphin NE, but only the beta-endorphin response is attenuated by pre-treatment with naloxone. Bulimics have decreased baseline levels NE, with normal responses of NE and augmented responses of heart rate to isoproterenol, suggesting decreased sympathetic neural activity and up-regulated cardiac beta-1 adrenoceptors. During surgical stress in adrenalectomized monkeys, enhanced sympathetic neural activity maintains circulatory homeostasis. Angiotensin II increases intracellular calcium and stimulates catecholamine release from cultured bovine adrenomedullary cells, providing the first demonstration that adrenomedullary cells contain functioning AII receptors.